PROJECT SUMMARY Quinonoid compounds are important building blocks in organic synthesis, and their diverse array of biological activity makes them attractive as potential drug candidates. However, asymmetric transformations of quinones have largely been limited to Diels?Alder cycloadditions. While the photochemistry of quinones has been extensively studied, efforts to render these reactions asymmetric have been unsuccessful. Photocycloadditions of quinones are of particular interest because they provide molecular scaffolds that are distinct from those accessible using traditional thermal chemistry. The development of asymmetric photocycloadditions of quinones will enable chemists to access medicinally relevant molecules and important synthetic intermediates for use in drug discovery. This proposal aims to accomplish this goal using visible light sensitization with transition metal photocatalysts. The ability to use visible light to effect triplet sensitization provides a practical, safer alternative to traditional photochemical methods, which require specialized photoreactors for the use of high energy UV light. The successful development of this methodology will enable organic chemists to synthesize enantioenriched quinone derivatives without using specialized equipment, greatly broadening accessibility. This methodology will provide a straightforward synthesis of biologically relevant structural motifs that were previously difficult to access, thereby offering opportunities for pharmaceutical development in unexplored chemical space.